A strain sensor, a stress detection device and a detection method thereof

Abstract

The present invention provides a strain sensor, a stress detection device and a detection method thereof, which relate to the field of stress detection, wherein the strain sensor comprises: a plurality of concave grooves and a protrusion structure are provided on a substrate; a permanent magnet is provided in the concave groove; a protrusion structure connects the left support and the right support; a resonator is perpendicular to the substrate and is provided between the left contact element and the right contact element; a first through hole is provided on the first platform of the left support and the first platform of the right support, and a support connecting bolt is used to pass through the first through hole to fix the left support and the right support on the protrusion structure; a second through hole is provided on the second platform of the left support and the second platform of the right support, and an adjusting bolt is used to pass through the second through hole to fasten the left contact element, the resonator and the right contact element to adjust the pressure between the right contact element and the resonator. The present invention can improve the stress detection accuracy, making the structural health detection of super-large structures more efficient and safer.

Description

Technical Field

[0001] The present invention relates to the field of stress detection, and in particular to a strain sensor, a stress detection device and a detection method thereof. Background Art

[0002] Large steel structures are constantly developing towards higher and more complex directions. Once an accident occurs, it will have a serious impact on the economy and society, but there is currently a lack of efficient means of structural health detection. In particular, super-large structures are steel frame structures with a height of more than 100 meters, such as Ferris wheels, transmission towers, viaducts, etc. The detection of such buildings is limited by their height and complexity, and it is almost impossible to detect them. At present, the detection of super-large structures is mostly traditional non-destructive testing by manual carrying of conventional testing equipment. The high-altitude operation is difficult and dangerous, and the equipment has a high deadweight, which is not suitable for super-large structures.

[0003] With the development of drones, the combination of detection equipment and drones has solved the inconvenience of manually carrying detection equipment. However, traditional strain gauges rely on cables to transmit signals and active wireless sensors require battery replacement. In addition, the horizontally placed resonators in existing similar sensors may cause the resonant frequency to increase first and then decrease due to installation errors, resulting in low accuracy of detection results. Summary of the invention

[0004] The object of the present invention is to provide a strain sensor, a stress detection device and a detection method thereof to solve the above-mentioned problems existing in the prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A strain sensor, comprising: a substrate arranged inside a shell, a permanent magnet, a resonator, a left contact element, a right contact element, a left support, a right support, a support connecting bolt and an adjusting bolt, and a receiving coil arranged outside the shell; the receiving coil is used to receive electromagnetic waves to provide energy for the resonator;

[0007] The base is provided with a plurality of concave grooves and protrusion structures; the permanent magnets are arranged in the concave grooves; the protrusion structures are used to connect the left support and the right support;

[0008] The resonator is perpendicular to the substrate and is disposed between the left contact element and the right contact element; the left contact element and the right contact element are ceramic sheets in contact with the positive electrode and the negative electrode of the resonator;

[0009] The left support is arranged on the left side of the left contact element, and the right support is arranged on the right side of the right contact element; a first through hole is provided on the first platform of the left support and the first platform of the right support, and the support connecting bolt is used to pass through the first through hole to fix the left support and the right support on the protrusion structure; a second through hole is provided on the second platform of the left support and the second platform of the right support, and the adjusting bolt is used to pass through the second through hole to tighten the left contact element, the resonator and the right contact element to adjust the pressure between the right contact element and the resonator.

[0010] Optionally, a contact surface between the right contact element and the resonator is an arc surface.

[0011] Optionally, the number and distribution of the permanent magnets determine the attractive force distribution of the permanent magnets;

[0012] The denser the distribution of the permanent magnets, the thinner the curing agent after curing; the fewer the distribution of the permanent magnets, the thicker the curing agent after curing.

[0013] A stress detection device, comprising: a drone interface, a device housing, a curing agent spraying device, a signal acquisition device, and a sensor ejection device;

[0014] The drone interface is provided on the top of the device housing and is used to realize electrical and mechanical connection between the drone and the stress detection device;

[0015] The curing agent spraying device, the signal acquisition device and the sensor ejection device are arranged inside the device housing; the sensor ejection device includes a plurality of strain sensors;

[0016] A third through hole is provided on the left side of the front end of the device shell, and the third through hole is used to fix the receiving coil of the signal acquisition device; three types of openings are provided on the right side of the front end of the device shell, among which the first type of opening is the ejection port of the magazine compartment of the sensor ejection device, the second type of opening is the opening at the end of the ejection connecting rod of the sensor ejection device, and the third type of opening is the fixing hole at the end of the curing agent duct of the curing agent spraying device.

[0017] Optionally, a permanent magnet adsorption unit is respectively embedded in the four corners of the front end of the device housing, and the permanent magnet adsorption unit is used to adsorb the stress detection device on the surface of the measured structure during the installation of the strain sensor.

[0018] Optionally, a fourth through hole is provided at the lower left side of the device housing, and the fourth through hole is used to expose the adjustable capacitor in the adjustment capacitor of the signal acquisition device.

[0019] Optionally, the sensor ejection device specifically includes: an ejection base plate, an ejection servo, a twisting connecting rod, an ejection connecting rod, a connecting rod rotating shaft, a magazine compartment, a magazine compression spring and a magazine push plate;

[0020] The ejection base plate is used to fix the ejection servo, the twisting connecting rod, the ejection connecting rod, the connecting rod rotating shaft, the magazine compartment, the magazine compression spring and the magazine push plate;

[0021] The ejection servo is used to rotate the ejection connecting rod, open the magazine compartment and release the strain sensor; the ejection servo is connected to the main control board in the signal acquisition device, and receives the rotation instruction through the data line connected to the drone; when the ejection servo receives the above rotation instruction, the main control board sends a PWM wave to the servo, and the duty cycle of the PWM wave determines the rotation angle of the ejection servo;

[0022] One end of the twisted link is connected to the ejection servo wheel, and the other end of the twisted link is connected to the end shaft of the ejection link; when the ejection servo rotates, the twisted link will drive the ejection link to rotate;

[0023] There is a rotating shaft at the end of the ejection connecting rod, so that the end rotating shaft of the ejection connecting rod can move freely; there is another rotating shaft at the front end of the ejection connecting rod that can only rotate but not translate; there is a protruding end at the front end of the ejection connecting rod, and the protruding end is used to prevent the strain sensor from detaching from the magazine compartment;

[0024] The connecting rod rotating shaft is used to fix the ejection connecting rod in the translation direction so that the ejection connecting rod rotates around the connecting rod rotating shaft;

[0025] The magazine compartment is located in the middle of the left and right ejection connecting rods. The magazine compartment is a rectangular parallelepiped with an open end. The left and right sides of the magazine compartment are provided with connecting holes, and the connecting holes are used to connect with the ejection base plate.

[0026] The ejection substrate is used to accommodate a plurality of strain sensors;

[0027] The ejection compression spring is located at the bottom of the magazine compartment opening. When the strain sensor is pressed into the bottom of the magazine compartment, the ejection spring is compressed. After the strain sensor at the front end of the magazine compartment pops out, the ejection spring pushes the remaining strain sensors forward to the magazine compartment opening until they are blocked by the protruding end of the ejection link.

[0028] The ejection push plate is located in the magazine compartment and outside the ejection spring, and is used to push the remaining strain sensor out of the magazine compartment after the ejection link is opened.

[0029] Optionally, the curing agent spraying device specifically includes: a spraying substrate, a linear motor, a linear motor rear baffle, a linear motor front baffle, a syringe barrel, a syringe rod, a syringe front baffle, a syringe rear baffle, a syringe rod baffle, and a curing agent conduit;

[0030] The spraying substrate is used to carry various components of the curing agent spraying device and connect the ejection substrate in the sensor ejection device with the main control substrate in the signal acquisition device; the components include a linear motor, a linear motor rear baffle, a linear motor front baffle, a syringe barrel, a syringe rod, a syringe front baffle, a syringe rear baffle, a syringe rod baffle and a curing agent conduit;

[0031] The front end of the linear motor is provided with a position-controllable telescopic push rod, and the front end of the telescopic push rod is connected to the rear end of the syringe rod baffle by bolts; the linear motor is fixed to the surface of the spraying substrate through the linear motor front baffle and the linear motor rear baffle; the linear motor front baffle has an opening for passing the telescopic push rod; the linear motor rear baffle has an opening for passing the tail signal line of the linear motor;

[0032] The syringe barrel and the syringe rod together form a syringe; the syringe is used to contain and spray a curing agent; the syringe barrel is used to contain a liquid and flowable curing agent, and the curing agent is used to bond the base of the strain sensor to the surface of the measured structure; the syringe rod is connected to the front end of the linear motor, and the front end piston of the syringe rod slides along the inner wall of the syringe barrel under the push of the syringe rod baffle;

[0033] The syringe front baffle and the syringe rear baffle are used to limit the movement of the syringe barrel; the syringe front baffle has a tapered hole matching the size of the front end of the syringe; the syringe rear baffle has a stepped hole, the inner diameter of the stepped surface of the stepped hole is larger than the outer diameter of the syringe barrel, the through hole of the stepped hole is smaller than the inner diameter of the syringe barrel, and the stepped hole is used to prevent the syringe barrel from sliding forward and backward;

[0034] The syringe rod baffle is used to connect the end of the syringe rod with the push rod of the linear motor;

[0035] One end of the curing agent conduit is connected to the front end opening of the syringe barrel, and the inner diameter of the curing agent conduit is smaller than the front end opening of the syringe; the other end of the curing agent conduit passes through the two through holes at the front end of the spray substrate and the two through holes on the right side of the front end of the device shell, and is led out of the device shell; the length of the curing agent conduit exposed from the device shell is less than the height of the permanent magnet on the device shell, so that the curing agent can flow out without being hindered by the structure being measured.

[0036] Optionally, the signal acquisition device specifically includes: a main control board substrate, a main control board, a support column and a transmitter;

[0037] The main control board substrate is connected to the main control board through the support column and is used to fix the main control board;

[0038] The main control board is used to control the linear motor of the curing agent spraying device, the ejection servo of the sensor ejection device and the network analyzer and receive the return signal;

[0039] The support column is used to fix the main control board on the surface of the main control board substrate;

[0040] The transmitter includes a network analyzer, an adjustment capacitor and a transmitting coil; the positive electrode of the output end of the network analyzer is connected to one end of the adjustment capacitor, the other end of the adjustment capacitor is connected to one end of the transmitting coil, and the other end of the transmitting coil is connected to the negative electrode of the output end of the network analyzer; the network analyzer is used to measure the reflection coefficient of the output end of the network analyzer after the transmitting coil is close to the receiving coil;

[0041] The adjusting capacitor includes one adjusting capacitor or a plurality of adjusting capacitors connected in parallel; the printed circuit board composed of the adjusting capacitor is fixed to the inner side of the housing of the device, and the adjusting knob of the adjusting capacitor is exposed from the housing; the adjusting capacitor is used to adjust the characteristic frequency of the transmitter so that the characteristic frequency of the transmitter is equal to the characteristic frequency of the strain sensor;

[0042] The transmitting coil is located outside the device housing and is used to generate an electromagnetic field to provide the strain sensor with energy required for detecting signals.

[0043] A detection method for a stress detection device, applied to the above-mentioned stress detection device, comprising:

[0044] Obtaining the initial characteristic frequency of the strain sensor;

[0045] Determine a preset starting frequency and a preset ending frequency according to the initial characteristic frequency;

[0046] Perform a frequency domain signal acquisition according to the preset starting frequency and the preset ending frequency to extract the first resonant frequency of the strain sensor;

[0047] Determine a detection start frequency and a detection end frequency according to the first resonant frequency;

[0048] Perform frequency domain signal acquisition again with the detection start frequency and the detection end frequency to generate a second resonant frequency; the accuracy of the second resonant frequency is higher than the accuracy of the first resonant frequency;

[0049] For a static structure, determining the stress of the measured structure according to the second resonant frequency;

[0050] For a dynamic structure, the maximum value and the minimum value of the fluctuation range of the second resonant frequency are determined, and the next frequency domain signal acquisition is performed to distinguish the stress of the measured structure in different time periods.

[0051] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: compared with the horizontally placed resonator in the existing similar sensors, the present invention places the resonator vertically on the substrate, and when the stress on the measured surface changes, the resonant frequency of the strain sensor changes monotonically, and the detection accuracy is higher;

[0052] In addition, through the drone interface, the signal is received by the signal acquisition device, and the curing agent spraying device and the sensor ejection device are controlled. It is suitable for non-contact stress detection of drones. Stress detection can be performed without replacing batteries, which solves the cable connection problem of wired sensors, the problem that existing passive wireless sensors are susceptible to electromagnetic interference, and the problem of unmanned installation and signal collection of sensors at high altitudes. This makes it possible for stress detection of super-large structures to be carried out without the need for people to install and detect stress sensors, making structural health detection of super-large structures more efficient and safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 It is the main view of the strain sensor;

[0055] Figure 2 It is a position relationship diagram of the left contact element, the resonator and the right contact element;

[0056] Figure 3 is a stereogram of the strain sensor;

[0057] Figure 4 This is the general assembly drawing of the stress detection device;

[0058] Figure 5 This is the closed state diagram of the sensor ejection device;

[0059] Figure 6 Open the state diagram for the sensor ejection device;

[0060] Figure 7 It is a top view of the sensor ejection device;

[0061] Figure 8 It is a three-dimensional diagram of a curing agent spraying device;

[0062] Fig. 9 is a schematic diagram of a syringe rod baffle;

[0063] Fig.10 It is a schematic diagram of the back baffle of the syringe;

[0064] Fig.11 It is a schematic diagram of the front baffle of the syringe;

[0065] Fig.12 It is a stereogram of the signal acquisition device;

[0066] Fig.13 It is the schematic diagram of the energy transmission system;

[0067] Fig.14 It is a schematic diagram of the use method of the non-contact stress detection device;

[0068] Fig.15 This is a flow chart of the non-contact stress detection signal acquisition method. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] The object of the present invention is to provide a strain sensor, a stress detection device and a detection method thereof, which can improve the stress detection accuracy and make the structural health detection of super-large structures more efficient and safer.

[0071] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] Example 1

[0073] like Figure 1-Figure 3 As shown, the present invention provides a strain sensor, comprising: a base 2 arranged inside a shell 1, a permanent magnet 3, a resonator 4, a left contact element 5, a right contact element 6, a left support 7, a right support 8, a support connecting bolt 9 and an adjusting bolt 10, and a receiving coil 11 arranged outside the shell 1; the receiving coil 11 is used to receive electromagnetic waves to provide energy for the resonator 4.

[0074] The base 2 is provided with a plurality of concave grooves and a protrusion structure; the permanent magnet 3 is provided in the concave groove; and the protrusion structure is used to connect the left support 7 and the right support 8 .

[0075] The resonator 4 is perpendicular to the substrate 2 and is disposed between the left contact element 5 and the right contact element 6 ; the left contact element 5 and the right contact element 6 are ceramic sheets in contact with the positive electrode and the negative electrode of the resonator 4 .

[0076] The left support 7 is arranged on the left side of the left contact element 5, and the right support 8 is arranged on the right side of the right contact element 6; a first through hole is provided on the first platform of the left support 7 and the first platform of the right support 8, and the support connecting bolt 9 is used to pass through the first through hole to fix the left support 7 and the right support 8 on the protruding structure; a second through hole is provided on the second platform of the left support 7 and the second platform of the right support 8, and the adjusting bolt 10 is used to pass through the second through hole to fasten the left contact element 5, the resonator 4 and the right contact element 6 to adjust the pressure between the right contact element 6 and the resonator 4.

[0077] In practical applications, the contact surface between the right contact element 6 and the resonator 4 is an arc surface.

[0078] In practical applications, the number and distribution of the permanent magnets 3 determine the distribution of the suction force of the permanent magnets 3 ; the denser the distribution of the permanent magnets 3 , the thinner the curing agent after curing; the fewer the distribution of the permanent magnets 3 , the thicker the curing agent after curing.

[0079] Furthermore, the resonator 4 is a quartz resonator 4, the resonant frequency is within the range of 10 MHz, and the thickness corresponds to 0.16 mm; in addition to the above-mentioned quartz resonator 4, the resonator 4 can also be other types of piezoelectric ceramics and piezoelectric crystals, and its resonant frequency covers the medium and high frequency range of 1 to 30 MHz.

[0080] Further, the left contact element 5 is made of alumina ceramics, with dimensions of 10 mm in length, 10 mm in width and 1 mm in thickness, and is used to support the electrode pins of the quartz resonator 4. Optionally, the left contact element 5 can be made of other hard, non-metallic materials including ceramics.

[0081] Further, the right contact element 6 is made of alumina ceramic, with a size of 6 mm in length and 6 mm in width, a square segment height of 1 mm, and a circular segment height of 0.25 mm, and is used to squeeze the quartz surface of the resonator 4 to change the resonant frequency of the resonator 4. Optionally, the circular segment of the right contact element 6 can be selected to have other heights, and the higher the height, the lower the stress sensitivity, and the lower the height, the higher the stress sensitivity. However, when the right contact element 6 does not have a circular segment, and contacts the quartz through the plane of the square segment, the stress sensitivity will be unstable and significantly reduced due to the line contact between the two.

[0082] In principle, the resonator 4 has an inherent vibration frequency, i.e., the resonance frequency. When its surface is compressed, its resonance frequency will change with the stiffness and damping of the compressed object. Generally speaking, the greater the stiffness of the right contact element 6, the greater the increase in the resonance frequency; the greater the damping, the higher the internal resistance, and the weaker the signal.

[0083] The substrate 2 is used to carry the sensitive elements of the sensor, including the resonator 4, the left contact element 5, and the right contact element 6. The bottom plane is bonded to the surface of the structure to be measured. In the embodiment, the four concave grooves protruding from the upper surface are used to accommodate the permanent magnet 3, and a higher rectangular protrusion on each side is used to connect the left support 7 and the right support 8.

[0084] Furthermore, the left support 7 and the right support 8 are used to fix the left contact element 5, the resonator 4, and the right contact element 6 above the substrate 2, and also serve to facilitate component assembly and adjust the surface pressure of the quartz plate; there are two vertical through holes on the sides of the above two elements, which are used to pass the support connecting bolts 9 and connect with the rectangular protrusions on both sides of the substrate 2.

[0085] Furthermore, the materials of the base 2, the left support 7, and the right support 8 can be selected from plastic or resin, which has the advantages of high flexibility and is not easy to crush the quartz plate in the resonator 4 due to large processing errors, but has the disadvantage of high viscoelasticity of the material, which causes the pressure on the quartz surface to be unable to recover immediately after the measured structure is strained and recovered; metal materials such as aluminum and steel can also be selected, which have the advantages of low viscoelasticity and the disadvantage of easy damage to quartz. Therefore, metal materials are used when the processing accuracy is high, and plastic and resin are used otherwise.

[0086] There are two through holes above the left support 7 and the right support 8, respectively, for passing the adjusting bolt 10 and its nut to adjust the pressure between the right contact element 6 and the resonator 4. The manufacturing tolerance between the components should ensure that there is a gap of several to tens of microns between the surface of the quartz plate and the vertex of the arc of the right contact element 6. By adjusting the pre-tightening force of the nut, the left support 7 and the right support 8 can be squeezed to reduce the above gap until the pressure is applied to the surface of the quartz plate.

[0087] The permanent magnets 3 are received in four grooves on the surface of the substrate 2, and are used to generate suction between the sensor substrate 2 and the ferromagnetic structure to be measured. Furthermore, the permanent magnets 3 can be selected from ferrite, neodymium iron boron, aluminum nickel cobalt, graphite, etc. The number and distribution of the permanent magnets 3 determine the distribution of the suction of the permanent magnets 3. The denser the permanent magnets 3, the thinner and more uniform the curing agent layer after curing; the fewer permanent magnets 3, for example, only on both sides, the thicker the middle curing agent will be after curing.

[0088] The opening of the housing is inverted on the base 2, and the components except the receiving coil 11 are wrapped inside to protect the resonator 4 from environmental influences, such as rain, dust, etc. Further, an airtight layer can be added inside the housing to prevent air from entering the inner cavity, which has the beneficial effect of reducing the oxidation rate of the quartz plate in the resonator 4 and isolating the influence of humidity on the sensor signal.

[0089] The receiving coil 11 is located at the top of the housing and is used to receive the electromagnetic waves emitted by the signal acquisition device 15, thereby providing energy to the resonator 4. Its inductance value is several microhenries. The signal after passing through the resonator 4 will be returned to the signal acquisition device 15 by the receiving coil 11, and the surface stress of the measured structure can be determined according to the change of the signal.

[0090] The usage and working principle of the strain sensor (hereinafter referred to as the detection sensor) are as follows.

[0091] 1) Before the sensor is packaged into the housing, two adjusting bolts 10 are passed through the through holes above the left support 7 and the right support 8, and the two pins of the resonator 4 are connected to the network analyzer 15-4 through a flexible wire. By rotating the nuts of the adjusting bolts 10 at the same time, the slit spacing between the left support 7 and the right support 8 can be reduced. When the measured resonant frequency of the resonator 4 begins to increase, it means that the arc surface of the contact element begins to contact the surface of the quartz plate. At this time, slowly adjust the nut until the resonant frequency increases by about 2kHz and the adjustment is completed.

[0092] 2) During the sensor packaging process, a curing agent is applied to the nut position of the adjustment bolt 10 that has been adjusted, so as to fix the nut to prevent the nut from loosening due to vibration and other reasons. After that, the sensor coil is fixed on the top of the housing, and two leads are passed through the through holes on the side of the housing to enter the housing and connect to the two pins of the resonator 4. Finally, the housing and the sensor coil are buckled on the substrate 2, and sealant is applied to the closed gap and the through hole through which the coil lead passes.

[0093] 3) When installing the sensor, apply an excess amount of curing agent on the surface of the steel structure to be installed. It is not necessary to apply it evenly. The installation direction of the sensor should follow the following rules. The direction of the line connecting the centers of the left support 7 and the right support 8 is the direction of stress change. At the same time, when installed vertically, the left support 7 is at the bottom and the right support 8 is at the top. Align the sensor with the area where the curing agent is applied and release the sensor when the base 2 is 2 to 5 mm away from the surface to be measured. The sensor base 2 will be pressed into the curing agent area under the magnetic force of the permanent magnet 3. The evenly distributed array of permanent magnets 3 will apply uniform pressure on the surface of the structure to be measured, thereby squeezing the uneven liquid curing agent into a thin and uniform coating. Finally, after the curing agent dries, the sensor base 2 will be permanently installed on the surface of the structure to be measured.

[0094] 4) When the mounting surface of the sensor is subjected to tensile stress in the horizontal direction of the mounting surface, or is subjected to a bending moment that causes the mounting surface of the sensor to bulge, the gap between the left support 7 and the right support 8 will increase, which will reduce the pressure on the surface of the resonator 4, causing the characteristic frequency of the sensor to decrease. Conversely, when the mounting surface of the sensor is subjected to compressive stress in the horizontal direction of the mounting surface, or is subjected to a bending moment that causes the mounting surface of the sensor to dent, the gap between the left support 7 and the right support 8 will decrease, which will increase the pressure on the surface of the resonator 4, causing the characteristic frequency of the sensor to increase.

[0095] 5) When the compressive stress on the surface of the structure or the bending moment that causes the surface to dent is too large, the resonator 4 will be crushed by the two contact units, causing the sensor to fail. Optionally, the higher the resonant frequency of the resonator 4, the smaller the impedance and the thinner the thickness, which will result in the sensor having a longer sensor distance and a lower tolerable pressure.

[0096] Example 2

[0097] like Figure 4 As shown, a stress detection device includes: a drone interface 12, a device housing 13, a curing agent spraying device 14, a signal acquisition device 15 and a sensor ejection device 16.

[0098] The drone interface 12 is provided on the top of the device housing 13 and is used to realize the electrical and mechanical connection between the drone and the stress detection device. Mechanically, the detection device is connected to the same-shaped interface at the end of the drone mechanical arm by bolts through the through holes on both sides of the drone interface 12; electrically, the cable passes through the through hole in the center of the drone interface 12 to realize the connection with the interface at the end of the drone mechanical arm.

[0099] The curing agent spraying device 14, the signal acquisition device 15 and the sensor ejection device 16 are arranged inside the device housing 13; the sensor ejection device 16 includes a plurality of strain sensors as shown in Example 1. The device housing 13 encloses the modules except the drone interface 12 and is connected to the drone interface 12 by bolts, such as Figure 4 As shown, there is a circular through hole on the left side of the front end of the device housing 13 for fixing the receiving coil 11 of the signal acquisition device 15 .

[0100] A third through hole is provided on the left side of the front end of the device housing 13, and the third through hole is used to fix the receiving coil 11 of the signal acquisition device 15; three types of openings are provided on the right side of the front end of the device housing 13, among which the first type of opening is the ejection port of the magazine compartment 16-6 of the sensor ejection device 16, the second type of opening is the opening at the end of the ejection connecting rod 16-4 of the sensor ejection device 16, and the third type of opening is the fixing hole at the end of the curing agent duct 14-10 of the curing agent spraying device 14.

[0101] Furthermore, the first type of opening, the second type of opening and the third type of opening are respectively square openings, narrow openings on upper and lower sides of the square opening and circular through holes on left and right sides of the narrow opening.

[0102] In practical applications, a permanent magnet 3 adsorption unit is embedded in the four corners of the front end of the device housing 13. The permanent magnet 3 adsorption unit is used to adsorb the stress detection device on the surface of the measured structure during the installation of the strain sensor to avoid sensor installation misalignment caused by the shaking of the drone.

[0103] Furthermore, there are three through holes on the top of the device housing 13 for mechanical connection with the drone interface 12 .

[0104] In practical applications, a fourth through hole is provided at the lower left side of the device housing 13, and the fourth through hole is used to expose the adjustable capacitor in the adjustment capacitor 15-5 of the signal acquisition device 15. There are two fourth through holes, and two adjustable capacitors in the adjustment capacitor 15-5 of the signal acquisition device 15 are exposed outside the module through the through holes, which is convenient for device debugging.

[0105] In practical applications, such as Figure 5-Figure 7 As shown, the sensor ejection device 16 specifically includes: an ejection base plate 16-1, an ejection servo 16-2, a twisting link 16-3, an ejection link 16-4, a link shaft 16-5, a magazine compartment 16-6, a magazine compression spring 16-7 and a magazine push plate 16-8.

[0106] The ejection base plate 16-1 is used to fix the ejection servo 16-2, the twisting link 16-3, the ejection link 16-4, the link shaft 16-5, the magazine compartment 16-6, the magazine compression spring 16-7 and the magazine push plate 16-8. Further, the ejection base plate 16-1 is a flat plate for fixing the above components, and the above components are only mechanically connected to the ejection base plate 16-1, so that the sensor ejection module can work independently.

[0107] The ejection servo 16-2 is used to rotate the ejection link 16-4, open the magazine compartment 16-6 and release the strain sensor; the ejection servo 16-2 is connected to the main control board 15-2 in the signal acquisition device 15, and receives the rotation command through the data line connected to the drone; when the ejection servo 16-2 receives the above rotation command, the main control board 15-2 sends a PWM wave to the servo, and the duty cycle of the PWM wave determines the rotation angle of the ejection servo 16-2. Further, the ejection servo 16-2 is a high-power servo with a rotation angle of 180 degrees and a precisely controllable rotation angle, which is used to rotate the ejection link 16-4, open the magazine compartment 16-6 and release the sensor. The maximum rotation angle of the ejection servo 16-2 is limited by the rear wall of the magazine compartment 16-6, and the maximum rotation angle just meets the size requirement that the sensor can be released from the magazine compartment 16-6.

[0108] One end of the twisted link 16-3 is connected to the rotating wheel of the ejection servo 16-2, and the other end of the twisted link 16-3 is connected to the terminal rotating shaft of the ejection link 16-4; when the ejection servo 16-2 rotates, the twisted link 16-3 will drive the ejection link 16-4 to rotate. Further, there are two twisted links 16-3, and when the servo rotates, the twisted link 16-3 will drive the ejection link 16-4 to rotate.

[0109] There is a rotating shaft at the end of the ejection link 16-4, so that the end rotating shaft of the ejection link 16-4 can move freely; there is another rotating shaft at the front end of the ejection link 16-4 that can only rotate but not translate; there is a protruding end at the front end of the ejection link 16-4, and the protruding end is used to prevent the strain sensor from detaching from the magazine compartment 16-6. Further, there are two ejection links 16-4.

[0110] The connecting rod rotating shaft 16-5 is used to fix the ejection connecting rod 16-4 in the translation direction so that the ejection connecting rod 16-4 rotates around the connecting rod rotating shaft 16-5. Further, there are two connecting rod rotating shafts 16-5.

[0111] When the ejection servo 16-2 rotates an angle, the free connection between the turntable and the twisting link 16-3 rotates and translates, driving the twisting link 16-3 to rotate. Since the link shaft 16-5 is fixed, the ejection link 16-4 will rotate under the drive of the twisting link 16-3, resulting in the end of the ejection link 16-4 rotating and translating toward the direction of the servo, and finally the protrusion at the front end of the ejection link 16-4 will separate to both sides, so that the magazine compartment 16-6 is opened.

[0112] The magazine compartment 16-6 is located in the middle of the left and right ejection links 16-4. The magazine compartment 16-6 is a rectangular parallelepiped with one end open. The left and right sides of the magazine compartment 16-6 are provided with connection holes, and the connection holes are used to connect with the ejection substrate 16-1. Further, the ejection substrate 16-1 can accommodate multiple sensors, and its size is determined by the sensor size and the number of sensors that need to be accommodated.

[0113] The ejection substrate 16 - 1 is used to accommodate a plurality of strain sensors.

[0114] The ejection compression spring is located at the bottom of the opening of the magazine compartment 16-6. When the strain sensor is pressed into the bottom of the magazine compartment 16-6, the ejection spring is compressed. After the strain sensor at the front end of the magazine compartment 16-6 is popped out, the ejection spring pushes the remaining strain sensors forward to the opening of the magazine compartment 16-6 until they are blocked by the protruding end of the ejection link 16-4.

[0115] The ejection push plate is located inside the magazine compartment 16-6 and outside the ejection spring, and is used to push the residual strain sensor outward toward the magazine compartment 16-6 after the ejection link 16-4 is opened. Further, the ejection push plate is smaller than the cross-section of the inner cavity of the magazine compartment 16-6 to avoid friction hindering the movement of the ejection push plate.

[0116] In practical applications, such as Figure 8-Figure 11 As shown, the curing agent spraying device 14 specifically includes: a spraying substrate 14-1, a linear motor 14-2, a linear motor rear baffle 14-3, a linear motor front baffle 14-4, a syringe barrel 14-5, a syringe rod 14-6, a syringe front baffle 14-7, a syringe rear baffle 14-8, a syringe rod baffle 14-9 and a curing agent conduit 14-10.

[0117] The spraying substrate 14-1 is used to carry various components of the curing agent spraying device 14 and connect the ejection substrate 16-1 in the sensor ejection device 16 with the main control substrate in the signal acquisition device 15; the components include a linear motor 14-2, a linear motor rear baffle 14-3, a linear motor front baffle 14-4, a syringe barrel 14-5, a syringe rod 14-6, a syringe front baffle 14-7, a syringe rear baffle 14-8, a syringe rod baffle 14-9 and a curing agent conduit 14-10. Further, the ejection substrate 16-1 is connected to the main control substrate in the signal acquisition device 15 through a through hole on the spraying substrate 14-1 and a bolt passing through the through hole.

[0118] The front end of the linear motor 14-2 is provided with a position-controllable telescopic push rod, and the front end of the telescopic push rod is connected to the rear end of the syringe rod baffle 14-9 by bolts; the linear motor 14-2 is fixed to the surface of the spray substrate 14-1 through the linear motor front baffle 14-4 and the linear motor rear baffle 14-3; the linear motor front baffle 14-4 has an opening for passing the telescopic push rod; the linear motor rear baffle 14-3 has an opening for passing the tail signal line of the linear motor 14-2.

[0119] The syringe barrel 14-5 and the syringe rod 14-6 together constitute a syringe; the syringe is used to contain and spray a curing agent; the syringe barrel 14-5 is used to contain a liquid and flowable curing agent, and the curing agent is used to bond the base 2 of the strain sensor to the surface of the structure to be measured; the syringe rod 14-6 is connected to the front end of the linear motor 14-2, and the front end piston of the syringe rod 14-6 slides along the inner wall of the syringe barrel 14-5 under the push of the syringe rod baffle 14-9.

[0120] The syringe front baffle 14-7 and the syringe rear baffle 14-8 are used to limit the movement of the syringe barrel 14-5; the syringe front baffle 14-7 has a conical hole matching the size of the front end of the syringe; the syringe rear baffle 14-8 has a step hole, the inner diameter of the step surface of the step hole is larger than the outer diameter of the syringe barrel 14-5, the through hole of the step hole is smaller than the inner diameter of the syringe barrel 14-5, and the step hole is used to prevent the syringe barrel 14-5 from sliding forward and backward.

[0121] The syringe rod baffle 14 - 9 is used to connect the end of the syringe rod 14 - 6 and the push rod of the linear motor 14 - 2 .

[0122] One end of the curing agent conduit 14-10 is connected to the front end opening of the syringe barrel 14-5, and the inner diameter of the curing agent conduit 14-10 is smaller than the front end opening of the syringe; the other end of the curing agent conduit 14-10 passes through the two through holes at the front end of the spray substrate 14-1 and the two through holes at the right side of the front end of the device housing 13, and is led out of the device housing 13; the length of the curing agent conduit 14-10 exposed from the device housing 13 is less than the height of the permanent magnet 3 on the device housing 13, so that the curing agent can flow out without being hindered by the structure being tested. Further, the material of the curing agent conduit 14-10 is hard plastic.

[0123] When the linear motor 14-2 receives the command from the main control board 15-2, its front push rod will move to the specified position and push the syringe rod baffle 14-9 and the syringe rod 14-6 to move forward. Since the syringe barrel 14-5 is fixed, the front piston of the syringe rod 14-6 will push the liquid curing agent in the syringe barrel 14-5 to flow outward. In this embodiment, the liquid curing agent is selected as a high-fluidity liquid with low viscosity, such as epoxy resin glue H610. The reason is that after the curing agent is sprayed from the curing agent conduit 14-10 to the surface of the structure to be measured, it will flow downward along the surface of the structure under the action of gravity to the position opposite to the sensor base 2, thereby achieving spraying. If a curing agent with a higher viscosity is needed, such as casting glue ergo9911, the curing agent will flow slowly after flowing out of the conduit and will not be able to cover the area where the sensor base 2 is located. To this end, the arrangement of the three sub-devices in the detection device needs to be adjusted, and the modification plan is as follows: first, the existing curing agent spraying device 14 is rotated 180 degrees at the existing position, so that the curing agent conduit 14-10 points to the rear of the new detection device; second, the opening of the curing agent conduit 14-10 extends downward, so that after the detection device rotates 180 degrees around the drone interface 12, the sensor base 2 coincides with the opening position of the curing agent conduit 14-10. During use, the detection device is rotated to the conduit opening forward, and the tested surface is adsorbed and glue is sprayed; then, the detection device is rotated 180 degrees so that the magazine compartment 16-6 opens forward, and is adsorbed again to the location where glue is applied, and the sensor is fired.

[0124] In practical applications, such as Fig.12 As shown, the signal acquisition device 15 specifically includes: a main control board substrate 15-1, a main control board 15-2, a support column 15-3 and a transmitter.

[0125] The main control board 15-2 substrate 15-1 is connected to the main control board 15-2 through the support column 15-3, which is used to fix the main control board 15-2. Further, the main control board 15-2 can be mechanically connected with other substrates through edge through holes.

[0126] The main control board 15-2 is used to control the linear motor 14-2 of the curing agent spraying device 14, the ejection servo 16-2 of the sensor ejection device 16, and the network analyzer 15-4 and receive the return signal. Further, the main control board 15-2 is a printed circuit board carrying a microprocessor, a power module, a motor drive module, and a serial communication module, and its function is to control the following modules and receive their return signals: the linear motor 14-2, the servo, and the network analyzer 15-4. When communicating with the linear motor 14-2, the input command is the moving position of the push rod of the linear motor 14-2, and the output data is the current position of the push rod of the linear motor 14-2. When communicating with the servo, the input command is the current rotation angle of the servo, and the output data is empty. When communicating with the network analyzer 15-4, the input data is the starting frequency, the end frequency, the number of data points, and the acquisition start command of the detection frequency domain, and the output data is the reflection coefficient of the transmitter circuit in the frequency domain within the detection frequency band. The main control board 15-2 is connected to the drone via the USB data transmission protocol and the 12V power line.

[0127] The support column 15 - 3 is used to fix the main control board 15 - 2 on the surface of the main control board 15 - 2 substrate 15 - 1 and to lift the back of the main control board 15 - 2 for a certain distance.

[0128] The transmitter includes a network analyzer 15-4, an adjustment capacitor 15-5 and a transmitting coil 15-6; the positive electrode of the output end of the network analyzer 15-4 is connected to one end of the adjustment capacitor 15-5, the other end of the adjustment capacitor 15-5 is connected to one end of the transmitting coil 15-6, and the other end of the transmitting coil 15-6 is connected to the negative electrode of the output end of the network analyzer 15-4, forming a closed loop; the network analyzer 15-4 is used to measure the reflection coefficient of the output end of the network analyzer 15-4 after the transmitting coil 15-6 is close to the receiving coil 11. Further, the network analyzer 15-4 calculates a plurality of frequency values ​​that increase in sequence according to the input starting frequency, ending frequency, and number of data points, and sequentially transmits AC excitation signals of different frequencies and detects the reflection coefficient of the output end. The network analyzer 15-4 is embedded in the groove at the bottom of the device housing 13.

[0129] The adjusting capacitor 15-5 includes one adjusting capacitor 15-5 or multiple adjusting capacitors 15-5 connected in parallel; the printed circuit board composed of the adjusting capacitor 15-5 is fixed to the inner side of the device housing 13, and the adjusting knob of the adjusting capacitor 15-5 is exposed from the housing; the adjusting capacitor 15-5 is used to adjust the characteristic frequency of the transmitter so that the characteristic frequency of the transmitter is equal to the characteristic frequency of the strain sensor, thereby increasing the power of the transmitter at the characteristic frequency. If the adjusting capacitor 15-5 does not exist in the transmitter, the characteristic frequency of the transmitter is much higher than the operating frequency of the resonator 4, which results in a larger resistance and a reflection coefficient close to zero.

[0130] The transmitting coil 15 - 6 is located outside the device housing 13 and is used to generate an electromagnetic field to provide the strain sensor with energy required for detecting signals.

[0131] The wireless communication principle between the passive wireless sensor and the transmitter is as follows: Fig.13 As shown, the sensor is composed of a receiving coil 11 and a bulk acoustic wave (BAW) stress sensor. The two ends of the lead of the receiving coil 11 are respectively connected to the two pins of the resonator 4 to form a closed loop.

[0132] When the network analyzer 15-4 generates an excitation signal of a frequency, the transmitting coil 15-6 will transmit an electromagnetic field in the opposite direction of its magnetic-repelling sheet. If the receiving coil 11 is within its magnetic field, an induced current will be generated in the sensor loop, which will cause the resonator 4 to vibrate mechanically and change the current value. The current passing through the resonator 4 in turn generates another electromagnetic field in the receiving coil 11, which is fed back to the transmitting coil 15-6, and finally changes the impedance in the transmitter.

[0133] When the network analyzer 15-4 generates a sweeping frequency excitation signal, the impedance of the transmitting coil 15-6 and the receiving coil 11 will change with the frequency, and the reflection coefficient curve corresponding to the above impedance is shaped like two superimposed parabolas. The transmitter characteristic signal is a parabola with a wider bandwidth, and the sensor characteristic signal is a parabola with a narrower bandwidth. This is because the transmitter composed of inductance and capacitance has a lower quality factor, while the sensor composed of resonator 4 and inductance has a higher quality factor. The frequencies at the apex of the parabolas of the sensor characteristic signal and the transmitter characteristic signal are called the sensor characteristic frequency and the transmitter characteristic frequency.

[0134] The beneficial effects of the passive wireless sensor include: moderate transmission distance, high resolution, and stable characteristic frequency. First, by adjusting the transmitter resonant frequency, the transmitter electromagnetic field strength near the sensor characteristic frequency is reduced, thereby increasing the signal transmission distance. Second, since the resonator 4 has an extremely high quality factor, the reflection coefficient changes significantly within a narrow frequency band, making it easy to identify changes in the characteristic frequency, thereby improving the resolution. Third, since the quality factor of the sensor is much higher than the quality factor of the transmitter, the characteristic frequency of the coupling system is significantly less affected by changes in the coupling degree, thereby having a more stable characteristic frequency.

[0135] In practical applications, the non-contact stress detection device is used as follows: Fig.14 shown.

[0136] The ultra-large structure high-altitude unmanned inspection platform consists of three parts, including a rotor drone, a side robotic arm, and a non-contact stress detection device.

[0137] The rotary wing UAV is used to carry the non-contact stress detection device close to a super-large structure surface located at a high altitude.

[0138] The lateral mechanical arm is located below the propeller on the side of the rotary wing drone, has multiple degrees of freedom, and its end joint can rotate horizontally 180 degrees, with a mechanical and electrical interface that matches the drone interface 12 on the top of the detection device. The size and length of the lateral mechanical arm should ensure that the drone can approach the running super-large equipment at a safe distance.

[0139] The non-contact stress detection device is as described above, and the drone interface 12 located at the top is connected to the lateral robotic arm and the motor interface through bolts.

[0140] The operating procedures of non-contact stress testing are as follows.

[0141] The drone takes off. The rotor drone takes off with the non-contact stress detection device, approaches the surface of the super-large structure to be tested, and hovers at a distance of 50-60 cm from the edge of the drone propeller to the surface to be tested. In this embodiment, the surface to be tested has the following requirements: First, the orientation of the surface of the structure to be tested can be a horizontal plane, an upward inclined plane, or a vertical plane, but cannot be facing downward. Second, the shape of the surface of the structure to be tested can be a plane, a circular surface, and a plane or a circular surface with a weld, but it cannot be a through-surface of a large-diameter cylinder and a small-diameter cylinder.

[0142] Optionally, if the sensor needs to be installed on an arc surface, a cylindrical surface with the same curvature as the mounting surface should be processed on the sensor base 2 so that the base 2 can completely fit the mounting surface. If the sensor needs to be installed directly above the weld, a horizontal groove protruding upwards needs to be designed at the center of the base 2 so that the horizontal groove can cross the weld and the planes on the left and right ends are connected to the surface of the structure to be measured.

[0143] Approaching the surface to be tested. The UAV extends the side robot arm toward the surface of the structure to be tested, so that the front end of the detection module approaches the surface of the structure to be tested, until the permanent magnet 3 in front of the device housing 13 is adsorbed around the target position.

[0144] Spraying curing agent. The drone sends a command to the detection module main control board 15-2, causing the push rod at the front end of the linear motor 14-2 to move forward quickly for a certain distance, which will cause the curing agent to be sprayed from the curing agent conduit 14-10 to the surface of the structure to be tested in front of the sensor substrate 2 to be installed below, and slowly stay along the surface of the structure until multiple columns of curing agent flow are formed.

[0145] Ejection sensor. The drone sends a command to the detection module main control board 15-2 to rotate the servo to a specified angle, which just makes the front end protrusion of the ejection link 16-4 move out to both sides of the magazine compartment 16-6. Since the sensor base 2 is always attracted by the structure to be tested and the permanent magnet 3 on the surface of the base 2, once the obstacles on both sides of the magazine compartment 16-6 are removed, it will be ejected to the surface where the curing agent has flowed under the action of the magnetic force. Under the action of the magnetic force, the curing agent will be pressed into a uniform film by the sensor base 2.

[0146] After the sensor ejection is completed, the UAV controls the mechanical arm to retreat horizontally, so that the permanent magnets 3 at the four corners of the device housing 13 are separated from the measured surface. During the separation process, the servo is controlled to reset, so that the protrusion at the front end of the ejection link 16-4 is stuck between the ejected sensor and the non-ejected sensor, which will leave the ejected sensor on the surface of the measured structure, while the non-ejected sensor base 2 is blocked by the ejection link 16-4.

[0147] Collect sensor signals. After the drone completes the sensor installation, it can detach from the structure to be tested and return to the ground or continue to install the remaining sensors. The curing time of the curing agent should be greater than 24 hours, after which the drone is controlled to take off and perform the test. By adjusting the drone positioning and the robotic arm, the sensing distance between the transmitting coil 15-6 and the sensing coil is 3 to 10 cm, and the two coils are made as concentric as possible.

[0148] In particular, since the sensor has a characteristic frequency that is not affected by the sensor distance, even if the drone is in a shaking state, the stress characteristics measured by the sensor can still be accurately extracted.

[0149] Even if the effect of drone jitter on the characteristic frequency is negligible, it still affects the amplitude of the reflected signal, which will lead to the appearance of frequency domain noise. To this end, two protruding magnetic adsorption supports can be installed on both sides of the detection module, and the front end of the magnetic adsorption support has a permanent magnet 3. After being adsorbed on the surface to be measured, the sensing coil and the transmitting coil 15-6 will be fixed values. Due to the fixation of the permanent magnet 3, the jitter of the drone will no longer have a significant effect on the sensing distance. The length of the magnetic adsorption support protruding from the front end of the detection end face should meet the requirement of a sensing distance of 3 to 10 cm. Since the magnetic adsorption support hinders the installation of the sensor, the magnetic adsorption support should be removed before the sensor is installed; the previously mentioned method can also be adopted to install the transmitting coil 15-6 on the back of the magazine compartment 16-6, and the drone interface 12 can be rotated 180 degrees to adjust the direction of the detection device toward the surface of the structure to be measured.

[0150] During the sensor acquisition process, the network analyzer 15-4 needs to perform parameter configuration to optimize the signal, and the steps are as shown in Example 3.

[0151] Example 3

[0152] A detection method for a stress detection device, applied to the stress detection device shown in Example 2, comprises:

[0153] Get the initial eigenfrequency of the strain sensor.

[0154] A preset start frequency and a preset end frequency are determined according to the initial characteristic frequency.

[0155] A frequency domain signal acquisition is performed according to the preset starting frequency and the preset ending frequency to extract the first resonant frequency of the strain sensor.

[0156] A detection start frequency and a detection end frequency are determined according to the first resonant frequency.

[0157] Frequency domain signal acquisition is performed again with the detection start frequency and the detection end frequency to generate a second resonant frequency; the accuracy of the second resonant frequency is higher than the accuracy of the first resonant frequency.

[0158] For a static structure, the stress of the measured structure is determined according to the second resonance frequency.

[0159] For a dynamic structure, the maximum value and the minimum value of the fluctuation range of the second resonant frequency are determined, and the next frequency domain signal acquisition is performed to distinguish the stress of the measured structure in different time periods.

[0160] In practical applications, non-contact stress detection signal acquisition methods are as follows Fig.15 As shown, the detection process of the stress detection device includes:

[0161] ①Record the initial characteristic frequency f of the sensor s,0 , and set the preset starting frequency f 1,0 and preset stop frequency f 2,0 Defined as:

[0162] f 1,0 =f s,0 -Δf (1)

[0163] f 2,0 =f s,0 +Δf (2)

[0164] Where Δf is the half frequency span, which is determined by the range in which the resonant frequency may occur.

[0165] ② Perform a frequency domain signal acquisition and extract the resonant frequency f of this sensor s,t , and reset the detection starting frequency f 1,t and detection end frequency f 2,t , respectively:

[0166] f 1,t =f s,t -Δf t (3)

[0167] f 2,t =f s,t +Δf t (4)

[0168] Where Δf t To determine the half-frequency bandwidth after the resonant frequency, the minimum value that can distinguish the resonant frequency should be met.

[0169] ③To detect the starting frequency f 1,t and detection end frequency f 2,t By collecting the starting frequency and the ending frequency again, the resonant frequency f can be measured with higher accuracy. s,t During this test, there is no need to reset f when repeating the characteristic frequency measurement. 1,t and f 2,t .

[0170] ④ In order to realize the periodic inspection of super-large structural stress, after the inspection, for the static structure, record the resonance frequency f s,t ; For dynamic structures, record the current resonance frequency f s,t The maximum and minimum values ​​of the fluctuation range. In the next acquisition, in order to distinguish the stress in different time periods, the subscript t increases by 1, and Δf does not change in the first acquisition.

[0171] The method for extracting the resonant frequency in the signal acquisition process is to extract the frequency domain signal data set (f, S 11 ) to smooth the curve, and then take the derivative of the smoothed curve to obtain the frequency domain first-order derivative data set (f,S 11 (1) ). The data set may have multiple frequencies, all of which make S 11 (1) Close to 0. To this end, the frequency domain second-order derivative data set (f, S 11 (2) ), then f s,t For S 11 (2) The frequency represented by the maximum positive value of .

[0172] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0173] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A stress detection device, characterized in that: include: UAV interface, device housing, curing agent spraying device, signal acquisition device and sensor ejection device; The drone interface is provided on the top of the device housing and is used to realize electrical and mechanical connection between the drone and the stress detection device; The curing agent spraying device, the signal acquisition device and the sensor ejection device are arranged inside the device housing; The sensor ejection device includes a plurality of strain sensors; the strain sensor includes: a base, a permanent magnet, a resonator, a left contact element, a right contact element, a left support, a right support, a support connecting bolt and an adjusting bolt arranged inside the shell, and a receiving coil arranged outside the shell; the receiving coil is used to receive electromagnetic waves to provide energy for the resonator; The base is provided with a plurality of concave grooves and protrusion structures; the permanent magnets are arranged in the concave grooves; the protrusion structures are used to connect the left support and the right support; The resonator is perpendicular to the substrate and is disposed between the left contact element and the right contact element; the left contact element and the right contact element are ceramic sheets in contact with the positive electrode and the negative electrode of the resonator; The left support is arranged on the left side of the left contact element, and the right support is arranged on the right side of the right contact element; a first through hole is arranged on the first platform of the left support and the first platform of the right support, and the support connecting bolt is used to pass through the first through hole to fix the left support and the right support on the protrusion structure; a second through hole is arranged on the second platform of the left support and the second platform of the right support, and the adjusting bolt is used to pass through the second through hole to fasten the left contact element, the resonator and the right contact element to adjust the pressure between the right contact element and the resonator; The sensor ejection device specifically includes: an ejection base plate, an ejection servo, a twisting connecting rod, an ejection connecting rod, a connecting rod rotating shaft, a magazine compartment, a magazine compression spring and a magazine push plate; The ejection base plate is used to fix the ejection servo, the twisting connecting rod, the ejection connecting rod, the connecting rod rotating shaft, the magazine compartment, the magazine compression spring and the magazine push plate; The ejection servo is used to rotate the ejection connecting rod, open the magazine compartment and release the strain sensor; the ejection servo is connected to the main control board in the signal acquisition device, and receives the rotation instruction through the data line connected to the drone; when the ejection servo receives the above rotation instruction, the main control board sends a PWM wave to the servo, and the duty cycle of the PWM wave determines the rotation angle of the ejection servo; One end of the twisted link is connected to the ejection servo wheel, and the other end of the twisted link is connected to the end shaft of the ejection link; when the ejection servo rotates, the twisted link will drive the ejection link to rotate; There is a rotating shaft at the end of the ejection connecting rod, so that the end rotating shaft of the ejection connecting rod can move freely; there is another rotating shaft at the front end of the ejection connecting rod that can only rotate but not translate; there is a protruding end at the front end of the ejection connecting rod, and the protruding end is used to prevent the strain sensor from detaching from the magazine compartment; The connecting rod rotating shaft is used to fix the ejection connecting rod in the translation direction so that the ejection connecting rod rotates around the connecting rod rotating shaft; The magazine compartment is located in the middle of the left and right ejection connecting rods. The magazine compartment is a rectangular parallelepiped with an open end. The left and right sides of the magazine compartment are provided with connecting holes, and the connecting holes are used to connect with the ejection base plate. The ejection substrate is used to accommodate a plurality of strain sensors; The magazine compression spring is located at the bottom of the magazine compartment opening, and when the strain sensor is pressed into the bottom of the magazine compartment, the magazine compression spring is compressed; after the strain sensor at the front end of the magazine compartment is ejected, the magazine compression spring pushes the remaining strain sensors forward to the magazine compartment opening until they are blocked by the protruding end of the ejection link; The magazine push plate is located in the magazine compartment and outside the magazine compression spring, and is used to push the remaining strain sensor out of the magazine compartment after the ejection link is opened; A third through hole is provided on the left side of the front end of the device shell, and the third through hole is used to fix the receiving coil of the signal acquisition device; three types of openings are provided on the right side of the front end of the device shell, among which the first type of opening is the ejection port of the magazine compartment of the sensor ejection device, the second type of opening is the opening at the end of the ejection connecting rod of the sensor ejection device, and the third type of opening is the fixing hole at the end of the curing agent duct of the curing agent spraying device.

2. The stress detection device according to claim 1, characterized in that: A permanent magnet adsorption unit is respectively embedded in the four corners of the front end of the device housing, and the permanent magnet adsorption unit is used to adsorb the stress detection device on the surface of the measured structure during the installation of the strain sensor.

3. The stress detection device according to claim 1, characterized in that: A fourth through hole is provided at the lower left side of the device housing, and the fourth through hole is used to expose the adjustable capacitor in the adjusting capacitor of the signal acquisition device.

4. The stress detection device according to claim 1, characterized in that: The curing agent spraying device specifically comprises: a spraying substrate, a linear motor, a linear motor rear baffle, a linear motor front baffle, a syringe barrel, a syringe rod, a syringe front baffle, a syringe rear baffle, a syringe rod baffle and a curing agent conduit; The spraying substrate is used to carry various components of the curing agent spraying device and connect the ejection substrate in the sensor ejection device with the main control substrate in the signal acquisition device; the components include a linear motor, a linear motor rear baffle, a linear motor front baffle, a syringe barrel, a syringe rod, a syringe front baffle, a syringe rear baffle, a syringe rod baffle and a curing agent conduit; The front end of the linear motor is provided with a position-controllable telescopic push rod, and the front end of the telescopic push rod is connected to the rear end of the syringe rod baffle by bolts; the linear motor is fixed to the surface of the spraying substrate through the linear motor front baffle and the linear motor rear baffle; the linear motor front baffle has an opening for passing the telescopic push rod; the linear motor rear baffle has an opening for passing the tail signal line of the linear motor; The syringe barrel and the syringe rod together form a syringe; the syringe is used to contain and spray a curing agent; the syringe barrel is used to contain a liquid and flowable curing agent, and the curing agent is used to bond the base of the strain sensor to the surface of the measured structure; the syringe rod is connected to the front end of the linear motor, and the front end piston of the syringe rod slides along the inner wall of the syringe barrel under the push of the syringe rod baffle; The syringe front baffle and the syringe rear baffle are used to limit the movement of the syringe barrel; the syringe front baffle has a tapered hole matching the size of the front end of the syringe; the syringe rear baffle has a stepped hole, the inner diameter of the stepped surface of the stepped hole is larger than the outer diameter of the syringe barrel, the through hole of the stepped hole is smaller than the inner diameter of the syringe barrel, and the stepped hole is used to prevent the syringe barrel from sliding forward and backward; The syringe rod baffle is used to connect the end of the syringe rod with the push rod of the linear motor; One end of the curing agent conduit is connected to the front end opening of the syringe barrel, and the inner diameter of the curing agent conduit is smaller than the front end opening of the syringe; the other end of the curing agent conduit passes through the two through holes at the front end of the spray substrate and the two through holes on the right side of the front end of the device shell, and is led out of the device shell; the length of the curing agent conduit exposed from the device shell is less than the height of the permanent magnet on the device shell, so that the curing agent can flow out without being hindered by the structure being measured.

5. The stress detection device according to claim 1, characterized in that: The signal acquisition device specifically includes: a main control board substrate, a main control board, a support column and a transmitter; The main control board substrate is connected to the main control board through the support column and is used to fix the main control board; The main control board is used to control the linear motor of the curing agent spraying device, the ejection servo of the sensor ejection device and the network analyzer and receive the return signal; The support column is used to fix the main control board on the surface of the main control board substrate; The transmitter includes the network analyzer, an adjustment capacitor and a transmitting coil; the positive electrode of the output end of the network analyzer is connected to one end of the adjustment capacitor, the other end of the adjustment capacitor is connected to one end of the transmitting coil, and the other end of the transmitting coil is connected to the negative electrode of the output end of the network analyzer; the network analyzer is used to measure the reflection coefficient of the output end of the network analyzer after the transmitting coil is close to the receiving coil; The adjusting capacitor includes one adjusting capacitor or a plurality of adjusting capacitors connected in parallel; the printed circuit board composed of the adjusting capacitor is fixed to the inner side of the housing of the device, and the adjusting knob of the adjusting capacitor is exposed from the housing; the adjusting capacitor is used to adjust the characteristic frequency of the transmitter so that the characteristic frequency of the transmitter is equal to the characteristic frequency of the strain sensor; The transmitting coil is located outside the device housing and is used to generate an electromagnetic field to provide the strain sensor with energy required for detecting signals.

6. A detection method of a stress detection device, characterized in that: The stress detection device according to any one of claims 1 to 5 comprises: Obtaining the initial characteristic frequency of the strain sensor; Determine a preset starting frequency and a preset ending frequency according to the initial characteristic frequency; Perform a frequency domain signal acquisition according to the preset starting frequency and the preset ending frequency to extract the first resonant frequency of the strain sensor; Determine a detection start frequency and a detection end frequency according to the first resonant frequency; Perform frequency domain signal acquisition again with the detection start frequency and the detection end frequency to generate a second resonant frequency; the accuracy of the second resonant frequency is higher than the accuracy of the first resonant frequency; For a static structure, determining the stress of the measured structure according to the second resonant frequency; For a dynamic structure, the maximum value and the minimum value of the fluctuation range of the second resonant frequency are determined, and the next frequency domain signal acquisition is performed to distinguish the stress of the measured structure in different time periods.

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